Evaluation of RU28318 and RU40555 as selective mineralocorticoid receptor and glucocorticoid receptor antagonists, respectively: receptor measures and functional studies

Abstract

Corticosterone regulates a wide range of physiological parameters. Two receptors for corticosterone have been identi®ed, the mineralocorticoid (type I) receptor (MR) and the glucocorticoid (type II) receptor (GR). To determine the relative role of these two receptors in mediating the effects of endogenous corticosterone, many studies have relied on the use of putative selective corticosteroid receptor antagonists. This study further examined the in vivo receptor selectivity of two compounds, RU28318 and RU40555 that are believed to be selective antagonists for MR and GR, respectively. Acute treatment of adrenalectomized rats with RU28318 (10±50 mg/kg) selectively decreased ex-vivo available MR binding in the hippocampus, whereas acute treatment with RU40555 (10±30 mg/kg) selectively decreased available GR binding in the hippocampus and pituitary. These receptor binding measures suggest that RU28318 in vivo selectively occupied MR, and that RU40555 in vivo selectively occupied GR. In functional studies, RU28318 (50 mg/kg) blocked the normalizing effect of aldosterone (120 m mg/kg) on saline intake of adrenalectomized rats. RU40555 (30 mg/kg) blocked the suppressive effect of dexamethasone (50 m mg/kg) on acute stress-induced corticosterone secretion. These studies further support the in vivo corticosteroid receptor selectivity of these two compounds and con®rms their effective corticosteroid antagonistic properties. #

Mineralocorticoid Receptor Antagonism Prevents the Electrical Remodeling That Precedes Cellular Hypertrophy After Myocardial Infarction

“…Although it interacts in vitro with the glucocorticoid receptor, RU28318 has been used as a selective MR antagonist because it is rapidly converted in vivo into its ␥-lactone form, which is highly selective for MR. 30 Infarct size was similar in the post-MI treated groups compared with untreated groups. RU28318 treatment did not have any effect on C m after 1 week (Figure 2A), whereas it blunted the increase in C m in post-MI myocytes 3 weeks after surgery.…”

Direct targeting of hippocampal neurons for apoptosis by glucocorticoids is reversible by mineralocorticoid receptor activation

“…Reasoning that this may have resulted from nanomolar (MR-activating) concentrations of levels of corticosterone in the culture medium, cells were exposed to two MR antagonists, SPIRO (a) and RU28318 (b); these compounds display slightly different pharmacological profiles. [33][34][35] In the absence of DEX, addition of SPIRO (10 À8 -10 À5 M) dose dependently increased the incidence of apoptosis (a); RU28318 at a dose of 10 À5 M also significantly stimulated apoptosis (b). In combination with the apoptosis noninducing dose of DEX (10 À6 M; a and b), all doses of SPIRO and RU28318 led to levels of cell death that were significantly greater than those seen after treatment with the antagonist alone, that is, blockade of MR with either SPIRO or RU28318 increased neuronal sensitivity to the apoptotic actions of DEX.…”

“…The less-potent MR antagonist oxprenoate (RU28318) [33][34][35] only stimulated apoptosis when used at 10 À5 M, the highest dose tested (Figure 4b). The apoptotic actions of SPIRO and RU28318 most probably result from their counteraction of the prosurvival effects of the nanomolar (MR-activating) levels of corticosterone in the B27/Neurobasal medium; these results indicate that tonic occupation of MR is essential for neuronal survival.…”

Endogenous Glucocorticoids Play a Positive Regulatory Role in the Anti-Keyhole Limpet Hemocyanin In Vivo Antibody Response

“…RU28386 (Roussel-UCLAF, Romainville, France; ␣-GCr type I) and RU40555 (Roussel-UCLAF, ␣-GRr type II) antagonists were dissolved in propylene glycol (1,2-propandediol, Fisher Scientific, Pittsburgh, PA) at doses of 50.0 mg/kg/2 ml and 30.0 mg/kg/ml, respectively. These doses have been previously reported to effectively antagonize CORT binding to both type I and type II receptors (22).…”